When you first
run PhotoToMesh you will see a large dialog with some greyed out controls
and two empty rectangles:

Drag an image
file into that dialog to get started (or use the File | Open) menu:

You will be presented
with a series of dialogs where you can change contrast, brightness, angle
and finally crop of the image:

In the above example
I've increased the contrast, as you can see comparing the two images.

The next dialog
lets you rotate the image, in this case there was no reason to change
the angle of the image so I left the rotation at 0, as you can see below:

Finally you can
crop the image to concentrate on an area of interest. In this case I've
done a small crop, compare the two images below.

At the end you
click on next and the image is placed inside PhotoToMesh (right panel
in the screenshot below) and the stereolithographic file can be viewed
(in the right panel):

Something to remember
as you play around with the sliders and numbers: Generally you need to
click on the "Recreate Model" button in the middle right of
the dialog to get the solid updated with the new parameters.

Also remember
that by dragging the mouse in the right-hand image you can view the model
at different angles.